At the moment, when a toolbar's buttons (or other controls) exceed the window width, the extra controls are "collected" in a sort of an expandable overflow mini-dialog, or multi-row box, accessible using an arrow-button at the end of the toolbar.

However - this is not the only way a toolbar could overflow. It could, instead, have multiple rows of controls, enough to fit all controls the toolbar contains.

(An example of the choice between several overflow alternatives can be found, for example, in the form of the Tab Mix Plus extension for Firefox; although browser tabs are not the same as toolbar controls.)

It would be nice to be able to choose that overflow mechanism. It would be especially useful if we want to facilitate newbies switching on and off the visibility of text labels next to button icons.